Processes for producing monoammonium succinate from fermentation broths containing diammonium succinate, monoammonium succinate and/or succinic acid, and conversion of monoammonium succinate to succinic acid

ABSTRACT

Processes for making monoammonium succinate (MAS) and/or succinic acid (SA) from either a clarified diammonium succinate (DAS)-containing fermentation broth or a clarified MAS-containing fermentation broth include (a) distilling the broth to form an overhead that includes water and optionally ammonia and a liquid bottoms that includes MAS or SA; (b) cooling and/or evaporating the bottoms and optionally adding an antisolvent to the bottoms to attain a temperature and composition sufficient to cause the bottoms to produce a solid portion that contains MAS or SA in contact with a liquid portion; (c) separating the solid portion from the liquid portion; and (d) recovering the solid portion.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Nos.61/317,799, filed Mar. 26, 2010, 61/320,053, filed Apr. 1, 2010, and61/329,742, filed Apr. 30, 2010, the subject matter of which is herebyincorporated by reference.

TECHNICAL FIELD

This disclosure relates to processes for the direct production ofmonoammonium succinate (MAS) from fermentation broths containingdiammonium succinate (DAS), MAS and/or succinic acid (SA). It alsorelates to the conversion of the MAS so obtained to SA.

BACKGROUND

Certain carbonaceous products of sugar fermentation are seen asreplacements for petroleum-derived materials for use as feedstocks forthe manufacture of carbon-containing chemicals. One such product is MAS.

SA can be produced by microorganisms using fermentable carbon sourcessuch as sugars as starting materials. However, most commercially viable,succinate producing microorganisms described in the literatureneutralize the fermentation broth to maintain an appropriate pH formaximum growth, conversion and productivity. Typically, the pH of thefermentation broth is maintained at or near a pH of 7 by introduction ofammonium hydroxide into the broth, thereby converting the SA to DAS.

Alternatively, the pH of the fermentation broth can be maintained at aselected value by introduction of sodium, potassium, or magnesium basesor mixtures thereof, including mixtures with ammonium bases. Theaddition of bases causes the SA to convert to other salts of SA. Otherbases may include K⁺, Na⁺ and Mg⁺², for example.

Kushiki (Japanese Published Patent Application, Publication No.2005-139156) discloses a method of obtaining MAS from an aqueoussolution of DAS that could be obtained from a fermentation broth towhich an ammonium salt is added as a counter ion. Specifically, MAS iscrystallized from an aqueous solution of DAS by adding acetic acid tothe solution to adjust the pH of the solution to a value between 4.6 and6.3, causing impure MAS to crystallize from the solution.

Masuda (Japanese Unexamined Application Publication P2007-254354, Oct.4, 2007) describes partial deammoniation of dilute aqueous solutions of“ammonium succinate” of the formula H₄NOOCCH₂CH₂COONH₄. From themolecular formula disclosed, it can be seen that “ammonium succinate” isdiammonium succinate. Masuda removes water and ammonia by heatingsolutions of the ammonium succinate to yield a solid SA-basedcomposition containing, in addition to ammonium succinate, at least oneof monoammonium succinate, succinic acid, monoamide succinate,succinimide, succinamide or ester succinate. Thus, it can be inferredthat like Kushiki, Masuda discloses a process that results in productionof impure MAS. The processes of both Kushiki and Masuda lead tomaterials that need to be subjected to various purification regimes toproduce high purity MAS.

It would be desirable to have a process for the direct production ofsubstantially pure MAS from a DAS, MAS, and/or SA-containingfermentation broth.

SUMMARY

We provide such a process by economically producing high purity MAS froma clarified DAS-containing fermentation broth. We thus provide a processfor making MAS from a clarified DAS-containing fermentation broth inwhich the DAS preferably constitutes at least 90 wt % of the totaldiammonium dicarboxylate salts contained in the broth, including (a)distilling the broth to form an overhead that comprises water andammonia, and a liquid bottoms that comprises MAS, at least some DAS, andat least about 20 wt % water; (b) cooling and/or evaporating thebottoms, and optionally adding an antisolvent to the bottoms, to attaina temperature and composition sufficient to cause the bottoms toseparate into a DAS-containing liquid portion and a MAS-containing solidportion that is substantially free of DAS; (c) separating the solidportion from the liquid portion; and (d) recovering the solid portion.

We also provide a process for making SA from a DAS-containingfermentation broth, including (a) distilling the broth to form a firstoverhead that includes water and ammonia, and a first liquid bottomsthat includes MAS, at least some DAS, and at least about 20 wt % water;(b) cooling and/or evaporating the bottoms, and optionally adding anantisolvent to the bottoms, to attain a temperature and compositionsufficient to cause the bottoms to separate into a DAS-containing liquidportion and a MAS-containing solid portion that is substantially free ofDAS; (c) separating the solid portion from the liquid portion; (d)recovering the solid portion; (e) dissolving the solid portion in waterto produce an aqueous MAS solution; (f) distilling the aqueous MASsolution at a temperature and pressure sufficient to form a secondoverhead that includes water and ammonia, and a second bottoms thatincludes a major portion of SA, a minor portion of MAS, and water; (g)cooling and/or evaporating the second bottoms to cause the secondbottoms to separate into a second liquid portion in contact with asecond solid portion that preferably consists essentially of SA and issubstantially free of MAS; (h) separating the second solid portion fromthe second liquid portion; and (i) recovering the second solid portion.

We further provide a process for making MAS from a clarifiedMAS-containing broth including (a) optionally, adding MAS, DAS, SA, NH₃,and/or NH₄ ⁺ to the broth to preferably maintain the pH of the brothbelow 6; (b) distilling the broth to form an overhead that includeswater and optionally ammonia, and a liquid bottoms that includes MAS, atleast some DAS, and at least about 20 wt % water; (c) cooling and/orevaporating the bottoms, and optionally adding an antisolvent to thebottoms, to attain a temperature and composition sufficient to cause thebottoms to separate into a DAS-containing liquid portion and aMAS-containing solid portion that is substantially free of DAS; (d)separating the solid portion from the liquid portion; and (e) recoveringthe solid portion.

We further yet provide a process for making SA from a clarifiedMAS-containing fermentation broth including (a) optionally, adding MAS,DAS, SA, NH₃, and/or NH₄ ⁺ to the broth to preferably maintain the pH ofthe broth below 6; (b) distilling the broth to form an overhead thatincludes water and optionally ammonia, and a liquid bottoms thatincludes MAS, at least some DAS, and at least about 20 wt % water; (c)cooling and/or evaporating the bottoms, and optionally adding anantisolvent to the bottoms, to attain a temperature and compositionsufficient to cause the bottoms to separate into a DAS-containing liquidportion and a MAS-containing solid portion that is substantially free ofDAS; (d) separating the solid portion from the liquid portion; and (e)recovering the solid portion; (f) dissolving the solid portion in waterto produce an aqueous MAS solution; (g) distilling the aqueous MASsolution at a temperature and pressure sufficient to form a secondoverhead that includes water and ammonia, and a second bottoms thatincludes a major portion of SA, a minor portion of MAS, and water; (h)cooling and/or evaporating the second bottoms to cause the secondbottoms to separate into a second liquid portion in contact with asecond solid portion that preferably consists essentially of SA and issubstantially free of MAS; (i) separating the second solid portion fromthe second liquid portion; and (j) recovering the second solid portion.

We additionally provide processes for making MXS from a clarifiedDAS-containing fermentation broth. Salts of succinic acid in theDAS-containing fermentation broth are converted to MXS to derive MXSfrom the fermentation broth, where MXS is monosodium succinate (MNaS)when a sodium (Na) base is used, monopotassium succinate (MKS) when apotassium (K) base is used, or MAS when an ammonia (NH₄ or NH₃) base isused. The process thus includes (a) distilling the broth to form anoverhead that comprises water and ammonia, and a liquid bottoms thatcomprises MXS, where X is at least one of NH₄ ⁺, Na and K, at least someDYS, where DYS includes DAS and at least one of disodium succinate(DNaS) and dipotassium succinate (DKS), and at least about 20 wt %water; (b) cooling and/or evaporating the bottoms, and optionally addingan antisolvent to the bottoms, to attain a temperature and compositionsufficient to cause the bottoms to separate into a DYS-containing liquidportion and a MXS-containing solid portion that is substantially free ofDYS; (c) separating the solid portion from the liquid portion; and (d)recovering the solid portion.

We further additionally provide a process for making MXS from aclarified MXS-containing broth, where X is at least one of NH₄ ⁺, Na andK including (a) optionally, adding at least one of SA, NH₃, NH₄ ⁺, Na⁺,and K⁺ to the broth to preferably maintain the pH of the broth below 6;(b) distilling the broth to form an overhead that includes water andoptionally ammonia, and a liquid bottoms that includes MXS, at leastsome DYS, where DYS includes at least one of DAS, DNaS and DKS, and atleast about 20 wt % water; (c) cooling and/or evaporating the bottoms,and optionally adding an antisolvent to the bottoms, to attain atemperature and composition sufficient to cause the bottoms to separateinto a DYS-containing liquid portion and a MXS-containing solid portionthat is substantially free of DYS; (d) separating the solid portion fromthe liquid portion; and (e) recovering the solid portion.

We also provide a process for making magnesium succinate (MgS) from aclarified DAS-containing fermentation broth including (a) distilling thebroth to form an overhead that includes water and ammonia, and a liquidbottoms that includes MgS, at least some DYS where DYS includes DAS andMgS and at least about 20 wt % water; (b) cooling and/or evaporating thebottoms, and optionally adding an antisolvent to the bottoms, to attaina temperature and composition sufficient to cause the bottoms toseparate into a DAS and MgS-containing liquid portion and anMgS-containing solid portion that is substantially free of DYS; (c)separating the solid portion from the liquid portion; and (d) recoveringthe solid portion.

We additionally provide a process for making MgS from a clarifiedMAS-containing fermentation broth including (a) optionally adding atleast one of SA, NH₃, NH₄ ⁺ and Mg²⁺ to the broth depending on pH of thebroth; (b) distilling the broth to form an overhead that comprises waterand optionally ammonia and a liquid bottoms that comprises MgS, at leastsome MAS, and at least about 20 wt % water; (c) cooling and/orevaporating the bottoms, and optionally adding an antisolvent to thebottoms, to attain a temperature and composition sufficient to cause thebottoms to separate into a MAS-containing liquid portion and aMgS-containing solid portion that is substantially free of MAS; (d)separating the solid portion from the liquid portion; and (e) recoveringthe solid portion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of one example of a process for making MASfrom a DAS containing broth.

FIG. 2 is a graph showing the solubility of MAS as a function oftemperature in both water and a 30% aqueous DAS solution.

FIG. 3 is a flow diagram showing selected aspects of our process.

FIG. 4 is a graph showing the mole fraction of MAS (HSu-), DAS (Su-2),and SA (H2Su) as a function of pH at 135° C.

FIG. 5 is a graph similar to that of FIG. 4 at 25° C.

FIG. 6 is a ternary diagram of MAS, DAS and water at selectedtemperatures.

FIG. 7 is a microphotograph of MAS crystals produced by our methods.

FIG. 8 is a microphotograph of SA crystals produced by our methods.

DETAILED DESCRIPTION

It will be appreciated that at least a portion of the followingdescription is intended to refer to representative examples of processesselected for illustration in the drawings and is not intended to defineor limit the disclosure, other than in the appended claims.

Our processes may be appreciated by reference to FIG. 1, which shows inblock diagram form one representative example, 10, of our methods.

A growth vessel 12, typically an in-place steam sterilizable fermentor,may be used to grow a microbial culture (not shown) that is subsequentlyutilized for the production of the DAS, MAS, and/or SA-containingfermentation broth. Such growth vessels are known in the art and are notfurther discussed.

The microbial culture may comprise microorganisms capable of producingSA from fermentable carbon sources such as carbohydrate sugars.Representative examples of microorganisms include, but are not limitedto, Escherichia coli (E. coli), Aspergillus niger, Corynebacteriumglutamicum (also called Brevibacterium flavum), Enterococcus faecalis,Veillonella parvula, Actinobacillus succinogenes, Mannheimiasucciniciproducens, Anaerobiospirillum succiniciproducens, PaecilomycesVarioti, Saccharomyces cerevisiae, Bacteroides fragilis, Bacteroidesruminicola, Bacteroides amylophilus, Alcaligenes eutrophus,Brevibacterium ammoniagenes, Brevibacterium lactofermentum, Candidabrumptii, Candida catenulate, Candida mycoderma, Candida zeylanoides,Candida paludigena, Candida sonorensis, Candida utilis, Candidazeylanoides, Debaryomyces hansenii, Fusarium oxysporum, Humicolalanuginosa, Kloeckera apiculata, Kluyveromyces lactis, Kluyveromyceswickerhamii, Penicillium simplicissimum, Pichia anomala, Pichia besseyi,Pichia media, Pichia guilliermondii, Pichia inositovora, Pichiastipidis, Saccharomyces bayanus, Schizosaccharomyces pombe, Torulopsiscandida, Yarrowia lipolytica, mixtures thereof and the like.

A preferred microorganism is an E. coli strain deposited at the ATCCunder accession number PTA-5132. More preferred is this strain with itsthree antibiotic resistance genes (cat, amphl, tetA) removed. Removal ofthe antibiotic resistance genes cat (coding for the resistance tochloramphenicol), and amphl (coding for the resistance to kanamycin) canbe performed by the so-called “Lambda-red (λ-red)” procedure asdescribed in Datsenko K A and Wanner B L., Proc. Natl. Acad. Sci. USA2000 Jun. 6; 97(12) 6640-5, the subject matter of which is incorporatedherein by reference. The tetracycline resistant gene tetA can be removedusing the procedure originally described by Bochner et al., J.Bacteriol. 1980 August; 143(2): 926-933, the subject matter of which isincorporated herein by reference. Glucose is a preferred fermentablecarbon source for this microorganism.

A fermentable carbon source (e.g., carbohydrates and sugars), optionallya source of nitrogen and complex nutrients (e.g., corn steep liquor),additional media components such as vitamins, salts and other materialsthat can improve cellular growth and/or product formation, and water maybe fed to the growth vessel 12 for growth and sustenance of themicrobial culture. Typically, the microbial culture is grown underaerobic conditions provided by sparging an oxygen-rich gas (e.g., air orthe like). Typically, an acid (e.g., sulphuric acid or the like) andammonium hydroxide are provided for pH control during the growth of themicrobial culture.

In one example (not shown), the aerobic conditions in growth vessel 12(provided by sparging an oxygen-rich gas) are switched to anaerobicconditions by changing the oxygen-rich gas to an oxygen-deficient gas(e.g., CO₂ or the like). The anaerobic environment triggersbioconversion of the fermentable carbon source to SA in situ in growthvessel 12. Ammonium hydroxide may be provided for pH control duringbioconversion of the fermentable carbon source to SA. The produced SA isat least partially neutralized to DAS due to the presence of theammonium hydroxide, leading to the production of a broth comprising DAS.The CO₂ provides an additional source of carbon for the production ofSA.

In another example, the contents of growth vessel 12 may be transferredvia stream 14 to a separate bioconversion vessel 16 for bioconversion ofa carbohydrate source to SA. An oxygen-deficient gas (e.g., CO₂ or thelike) is sparged in bioconversion vessel 16 to provide anaerobicconditions that trigger production of SA. Ammonium hydroxide is providedfor pH control during bioconversion of the carbohydrate source to SA.Due to the presence of the ammonium hydroxide, the SA produced is atleast partially neutralized to DAS, leading to production of a broththat comprises DAS. The CO₂ provides an additional source of carbon forproduction of SA.

In another example, the bioconversion may be conducted at relatively lowpH (e.g., 3-6). A base (ammonium hydroxide or ammonia) may be providedfor pH control during bioconversion of the carbohydrate source to SA.Depending on the desired pH, due to the presence or lack of the ammoniumhydroxide, either SA is produced or the SA produced is at leastpartially neutralized to MAS, DAS, or a mixture comprising SA, MASand/or DAS. Thus, the SA produced during bioconversion can besubsequently neutralized, optionally in an additional step, by providingeither ammonia or ammonium hydroxide leading to a broth comprising DAS.As a consequence, a “DAS-containing fermentation broth” generally meansthat the fermentation broth comprises DAS and possibly any number ofother components such as MAS and/or SA, whether added and/or produced bybioconversion or otherwise. Similarly, a “MAS-containing fermentationbroth” generally means that the fermentation broth comprises MAS andpossibly any number of other components such as DAS and/or SA, whetheradded and/or produced by bioconversion or otherwise.

The broth resulting from the bioconversion of the fermentable carbonsource (in either vessel 12 or vessel 16, depending on where thebioconversion takes place), typically contains insoluble solids such ascellular biomass and other suspended material, which are transferred viastream 18 to clarification apparatus 20 before distillation. Removal ofinsoluble solids clarifies the broth. This reduces or prevents foulingof subsequent distillation equipment. The insoluble solids can beremoved by any one of several solid-liquid separation techniques, aloneor in combination, including but not limited to centrifugation andfiltration (including, but not limited to ultra-filtration,micro-filtration or depth filtration). The choice of filtrationtechnique can be made using known techniques. Soluble inorganiccompounds can be removed by any number of known methods such as but notlimited to ion-exchange, physical adsorption.

An example of centrifugation is a continuous disc stack centrifuge. Itmay be useful to add a polishing filtration step followingcentrifugation such as dead-end or cross-flow filtration that mayinclude the use of a filter aide such as diatomaceous earth or the like,or more preferably ultra-filtration or micro-filtration. Theultra-filtration or micro-filtration membrane can be ceramic orpolymeric, for example. One example of a polymeric membrane is SelROMPS-U20P (pH stable ultra-filtration membrane) manufactured by KochMembrane Systems (850 Main Street, Wilmington, Mass., USA). This is acommercially available polyethersulfone membrane with a 25,000 Daltonmolecular weight cut-off which typically operates at pressures of 0.35to 1.38 MPa (maximum pressure of 1.55 MPa) and at temperatures up to 50C. As an alternative to using centrifugation and a polishing filtrationin combination, cross-flow filtration may be employed alone using ultra-or micro-filtration membranes.

The resulting clarified DAS-containing broth or MAS-containing broth,substantially free of the microbial culture and other solids, istransferred via stream 22 to distillation apparatus 24.

The clarified broth should contain DAS and/or MAS in an amount that isat least a majority of, preferably at least about 70 wt %, morepreferably 80 wt % and most preferably at least about 90 wt % of all theammonium dicarboxylate salts in the broth. The concentration of DASand/or MAS as a weight percent (wt %) of the total dicarboxylic acidsalts in the fermentation broth can be easily determined by highpressure liquid chromatography (HPLC) or other known means.

Water and ammonia are removed from distillation apparatus 24 as anoverhead, and at least a portion is optionally recycled via stream 26 tobioconversion vessel 16 (or growth vessel 12 operated in the anaerobicmode). Distillation temperature and pressure are not critical as long asthe distillation is carried out in a way that ensures that thedistillation overhead contains water and ammonia, and the distillationbottoms preferably comprises at least some DAS and at least about 20 wt% water. A more preferred amount of water is at least about 30 wt % andan even more preferred amount is at least about 40 wt %. The rate ofammonia removal from the distillation step increases with increasingtemperature and also can be increased by injecting steam (not shown)during distillation. The rate of ammonia removal during distillation mayalso be increased by conducting distillation under a vacuum, underpressure or by sparging the distillation apparatus with a non-reactivegas such as air, nitrogen or the like.

Removal of water during the distillation step can be enhanced by the useof an organic azeotroping agent such as toluene, xylene, hexane,cyclohexane, methyl cyclohexane, methyl isobutyl ketone, heptane or thelike, provided that the bottoms contains at least about 20 wt % water.If the distillation is carried out in the presence of an organic agentcapable of forming an azeotrope consisting of the water and the agent,distillation produces a biphasic bottoms that comprises an aqueous phaseand an organic phase, in which case the aqueous phase can be separatedfrom the organic phase, and the aqueous phase used as the distillationbottoms. Byproducts such as succinamide and succinimide aresubstantially avoided provided the water level in the bottoms ismaintained at a level of at least about 30 wt %.

A preferred temperature for the distillation step is in the range ofabout 50 to about 300° C., depending on the pressure. A more preferredtemperature range is about 90 to about 150° C., depending on thepressure. A distillation temperature of about 110 to about 140° C. ispreferred. “Distillation temperature” refers to the temperature of thebottoms (for batch distillations this may be the temperature at the timewhen the last desired amount of overhead is taken).

Adding a water miscible organic solvent or an ammonia separating solventmay facilitate deammoniation over a variety of distillation temperaturesand pressures as discussed above. Such solvents can include aprotic,bipolar, oxygen-containing solvents that may be able to form passivehydrogen bonds. Examples include, but are not limited to, diglyme,triglyme, tetraglyme, propylene glycol, sulfoxides such asdimethylsulfoxide (DMSO), amides such as dimethylformamide (DMF) anddimethylacetamide, sulfones such as dimethylsulfone, sulfolane,polyethyleneglycol (PEG), butoxytriglycol, N-methylpyrolidone (NMP),gamma butyrolactone, ethers such as dioxane, methyl ethyl ketone (MEK)and the like. Such solvents aid in the removal of ammonia from the DASor MAS in the clarified broth. Regardless of the distillation technique,it is preferable that the distillation be carried out in a way thatensures that at least some DAS and at least about 20 wt % water remainin the bottoms and even more advantageously at least about 30 wt %.

The distillation can be performed at atmospheric, sub-atmospheric orsuper-atmospheric pressures. The distillation can be a one-stage flash,a multistage distillation (i.e., a multistage column distillation) orthe like. The one-stage flash can be conducted in any type of flasher(e.g., a wiped film evaporator, thin film evaporator, thermosiphonflasher, forced circulation flasher and the like). The multistages ofthe distillation column can be achieved by using trays, packing or thelike. The packing can be random packing (e.g., Raschig rings, Pallrings, Berl saddles and the like) or structured packing (e.g.,Koch-Sulzer packing, Intalox packing, Mellapak and the like). The trayscan be of any design (e.g., sieve trays, valve trays, bubble-cap traysand the like). The distillation can be performed with any number oftheoretical stages.

If the distillation apparatus is a column, the configuration is notparticularly critical, and the column can be designed using well knowncriteria. The column can be operated in either stripping mode,rectifying mode or fractionation mode. Distillation can be conducted ineither batch or continuous mode. In the continuous mode, the broth maybe fed continuously into the distillation apparatus, and the overheadand bottoms may be continuously removed from the apparatus as they areformed. The distillate from distillation is an ammonia/water solution,and the distillation bottoms is a liquid, aqueous solution of MAS andDAS, which may also contain other fermentation by-product salts (i.e.,ammonium acetate, ammonium formate, ammonium lactate and the like) andcolor bodies.

The distillation bottoms can be transferred via stream 28 to coolingapparatus 30 and cooled by conventional techniques. Cooling technique isnot critical, although a preferred technique will be described below. Aheat exchanger (with heat recovery) can be used. A flash vaporizationcooler can be used to cool the bottoms down to about 15° C. Cooling to0° C. typically employs a refrigerated coolant such as, for example,glycol solution or, less preferably, brine. A concentration step can beincluded prior to cooling to help increase product yield. Further, bothconcentration and cooling can be combined using methods known such asvacuum evaporation and heat removal using integrated cooling jacketsand/or external heat exchangers.

We found that the presence of some DAS in the liquid bottoms facilitatescooling-induced separation of the bottoms into a liquid portion incontact with a solid portion that at least “consists essentially” of MAS(meaning that the solid portion is at least substantially purecrystalline MAS) by reducing the solubility of MAS in the liquid,aqueous, DAS-containing bottoms. FIG. 2 illustrates the reducedsolubility of MAS in an aqueous 30 wt % DAS solution at varioustemperatures ranging from 0 to 60° C. The upper curve shows that even at0° C. MAS remains significantly soluble in water (i.e., about 20 wt % inaqueous solution). The lower curve shows that at 0° C. MAS isessentially insoluble in a 30 wt % aqueous DAS solution. We discovered,therefore, that MAS can be more completely crystallized out of anaqueous solution if some DAS is also present in that solution. Apreferred concentration of DAS in such a solution is in the ppm to about3 wt % range. This allows crystallization of MAS (i.e., formation of thesolid portion of the distillation bottoms) at temperatures higher thanthose that would be required in the absence of DAS.

When about 50% of the ammonia is removed from DAS contained in anaqueous medium the succinate species establish an equilibrium molardistribution that is about 0.1:0.8:0.1 in DAS:MAS:SA within a pH rangeof 4.8 to 5.4, depending on the operating temperature and pressure. Whenthis composition is concentrated and cooled, MAS exceeds its solubilitylimit in water and crystallizes. When MAS undergoes a phase change tothe solid phase, the liquid phase equilibrium resets thereby producingmore MAS (DAS donates an ammonium ion to SA). This causes more MAS tocrystallize from solution and continues until appreciable quantities ofSA are exhausted and the pH tends to rise. As the pH rises, the liquidphase distribution favors DAS. However, since DAS is highly soluble inwater, MAS continues to crystallize as its solubility is lower than DAS.In effect, the liquid phase equilibrium and the liquid-solid equilibriaof succinate species act as a “pump” for MAS crystallization, therebyenabling MAS crystallization in high yield.

In addition to cooling, evaporation, or evaporative cooling describedabove, crystallization of MAS can be enabled and/or facilitated byaddition of an antisolvent. In this context, antisolvents may besolvents typically miscible with water, but cause crystallization of awater soluble salt such as MAS due to lower solubility of the salt inthe solvent. Solvents with an antisolvent effect on MAS can be alcoholssuch as ethanol and propanol, ketones such as methyl ethyl ketone,ethers such as tetrahydrofuran and the like. The use of antisolvents isknown and can be used in combination with cooling and evaporation orseparately.

The distillation bottoms, after cooling in unit 30, is fed via stream 32to separator 34 for separation of the solid portion from the liquidportion. Separation can be accomplished via pressure filtration (e.g.,using Nutsche or Rosenmond type pressure filters), centrifugation andthe like. The resulting solid product can be recovered as product 36 anddried, if desired, by standard methods.

After separation, it may be desirable to treat the solid portion toensure that no liquid portion remains on the surface(s) of the solidportion. One way to minimize the amount of liquid portion that remainson the surface of the solid portion is to wash the separated solidportion with water and dry the resulting washed solid portion (notshown). A convenient way to wash the solid portion is to use a so-called“basket centrifuge” (not shown). Suitable basket centrifuges areavailable from The Western States Machine Company (Hamilton, Ohio, USA).

The liquid portion of the separator 34 (i.e., the mother liquor) maycontain remaining dissolved MAS, any unconverted DAS, any fermentationbyproducts such as ammonium acetate, lactate, or formate, and otherminor impurities. This liquid portion can be fed via stream 38 to adownstream apparatus 40. In one instance, apparatus 40 may be a meansfor making a de-icer by treating in the mixture with an appropriateamount of potassium hydroxide, for example, to convert the ammoniumsalts to potassium salts. Ammonia generated in this reaction can berecovered for reuse in the bioconversion vessel 16 (or growth vessel 12operating in the anaerobic mode). The resulting mixture of potassiumsalts is valuable as a de-icer and anti-icer.

The mother liquor from the solids separation step 34, can be recycled(or partially recycled) to distillation apparatus 24 via stream 42 tofurther enhance recovery of MAS, as well as further convert DAS to MAS.

The solid portion of the cooling-induced crystallization issubstantially pure MAS and is, therefore, useful for the known utilitiesof MAS.

HPLC can be used to detect the presence of nitrogen-containingimpurities such as succinamide and succinimide. The purity of MAS can bedetermined by elemental carbon and nitrogen analysis. An ammoniaelectrode can be used to determine a crude approximation of MAS purity.

Depending on the circumstances and various operating inputs, there areinstances when the fermentation broth may be a clarified MAS-containingfermentation broth or a clarified SA-containing fermentation broth. Inthose circumstances, it can be advantageous to optionally add MAS, DAS,SA, ammonia, and/or ammonium hydroxide to those fermentation broths tofacilitate the production of substantially pure MAS. For example, theoperating pH of the fermentation broth may be oriented such that thebroth is a MAS-containing broth or a SA-containing broth. MAS, DAS, SA,ammonia, and/or ammonium hydroxide may be optionally added to thosebroths to attain a broth pH preferably <6 to facilitate production ofthe above-mentioned substantially pure MAS. Also, it is possible thatMAS, DAS and/or SA from other sources may be added as desired. In oneparticular form, it is especially advantageous to recycle MAS, DAS andwater from the liquid bottoms resulting from the distillation step 24,and/or the liquid portion from the separator 34, into the fermentationbroth. In referring to the MAS-containing broth, such broth generallymeans that the fermentation broth comprises MAS and possibly any numberof other components such as DAS and/or SA, whether added and/or producedby bioconversion or otherwise.

The solid portion can be converted into SA by removing ammonia. This canbe carried out as follows. The solid portion (consisting essentially ofMAS) obtained from any of the above-described conversion processes canbe dissolved in water to produce an aqueous MAS solution. This solutioncan then be distilled at a temperature and pressure sufficient to forman overhead that comprises water and ammonia, and a bottoms thatcomprises a major portion of SA, a minor portion of MAS and water. Thebottoms can be cooled to cause it to separate into a liquid portion incontact with a solid portion that consists essentially of SA and issubstantially free of MAS. The solid portion can be separated from thesecond liquid portion and recovered as substantially pure SA, asdetermined by HPLC.

Turning to FIG. 3, we describe one of our particularly preferredprocesses. In FIG. 3, a stream 100 of DAS, which may be a stream ofclarified fermentation broth which contains DAS (among other things), issubjected to reactive evaporation/distillation in distillation column102. The distillation may occur over a range of temperatures such asabout 110 to about 145° C., preferably about 135° C. The pressure in thedistillation column 102 can be over a broad range about 1.5 to about 4bar, preferably about 3.5 bar. Water and ammonia are separated indistillation column 102 and form an overhead 104. The liquid bottoms 106comprises MAS, at least some DAS and at least about 20 wt % water.Typically, bottoms 106 contains about 5 to about 20 wt % MAS, about 80wt % to about 95 wt % water and about 1 to about 3 wt % DAS. The pH ofthe bottoms may be in a range of about 4.6 to about 5.6.

The bottoms 106 is streamed to a concentrator 108 which removes watervia overhead stream 110. Concentrator 108 can operate over a range oftemperatures such as about 90° C. to about 110° C., preferably about100° C. and over a range of pressures such as at about 0.9 bar to about1.2 bar, preferably about 1.103 bar.

Concentrator 108 produces a bottoms stream 112 which typically containsabout 40 wt % to about 70 wt %, preferably about 55 wt % MAS. Hence, theconcentrator concentrates the amount of MAS typically by about 2 toabout 11 times, preferably about 4 times to about 6 times.

Bottoms stream 112 flows to a first crystallizer 114 which operates at atemperature typically at about 50 to about 70° C., preferably about 60°C. A water overhead stream 116 is produced by the crystallizer. Bottoms118 flows to a centrifuge 120 which produces a solid stream 122 whichtypically has a yield of MAS of about 95%. A remaining liquid flow 124is sent to a second crystallizer 126 which removes additional water byway of overhead stream 128 and operates at a temperature typically atabout 30 to about 50° C., preferably about 40° C. The bottoms stream 130flows to a centrifuge 132. Centrifuge produces a solid stream 134 whichis redissolved with a water stream 136 which introduces water in atemperature range typically of about 70 to about 90° C., preferablyabout 90° C. That stream flows to a first mixer 138 and produces a firstrecycle flow 140 back to the first crystallizer 114.

Remaining liquid from centrifuge 132 flows via stream 141 to thirdcrystallizer 142 which produces an overhead stream 144 of water. Thirdcrystallizer 132 typically operates at a temperature of about 10 toabout 30° C., typically about 20° C. The remaining bottoms flow 146streams to a third centrifuge 148 and solid material produced by thirdcentrifuge 148 flows to a second mixer 150 by way of stream 152. Thatsolid stream is dissolved by a second water stream 154 which introduceswater typically at a temperature range of about 50 to about 70° C.,preferably about 70° C. Second mixer 150 produces a recycle stream 156which is recycled to second crystallizer 126. Remaining material flowsoutwardly of the system from third centrifuge 148 by way of purge stream158 which typically represents about 5 wt % of the total MAS containedin stream 112. It is understood that the desired crystallizationtemperatures in crystallizers 114, 126, and 142 can be attained byevaporation (as depicted), or by indirect contact with an externalcooling medium, or a combination thereof.

FIG. 4 is a graph showing the mole fraction of MAS, DAS and SA as afunction of pH at 135° C., which is typical of the temperature indistillation column 102 of FIG. 3. FIG. 5 is the same as FIG. 4 exceptfor a temperature at 25° C. Those figures show the relative proportionsof the three components depending on the pH at the particulartemperature. In accordance with our methods, the typical operating pH ofthe reactive evaporation/distillation unit 102 and the concentrationunit 108 may be about 5.3 leading to maximum production of MAS. Whenabout 50% of the ammonia is removed from DAS contained in an aqueousmedium the succinate species establish an equilibrium molar distributionthat is about 0.1:0.8:0.1 in DAS:MAS:SA within a pH range of about 4.8to about 5.4, depending on the operating temperature and pressure.Without being bound by any particular theory, we believe that when thiscomposition is concentrated and cooled, MAS exceeds its solubility limitin water and crystallizes. Also, when MAS undergoes a phase change tothe solid phase, the liquid phase equilibrium is believed todeliberately reset, thereby producing more MAS (DAS donates an ammoniumion to SA). We believe that this causes more MAS to crystallize fromsolution and continues until appreciable quantities of SA are exhaustedand the pH tends to rise. As the pH rises, the liquid phase distributionfavors DAS. However, since DAS is highly soluble in water, MAS continuesto crystallize as its solubility is lower than DAS. In effect, theliquid phase equilibrium and the liquid-solid equilibria of succinatespecies act as a “pump” for MAS crystallization, thereby enabling MAScrystallization in high yield.

FIG. 6 is a ternary diagram of MAS, DAS and water at three differenttemperatures, namely 20° C., 35° C. and 60° C. This diagram isillustrative of the solid-liquid equilibrium that causes crystallizationof pure MAS or DAS at different temperatures. We constructed FIG. 6 withexperimental solubility data which shows that if a liquid compositioncontaining MAS, DAS, and water is cooled to cause the separation of asolid portion and if the liquid composition lies to the left of theeutectic points identified as “A,” then liquid-solid equilibriumprinciples suggest that the solid portion will be pure MAS. Conversely,if a liquid composition containing MAS, DAS, and water is cooled tocause the separation of a solid portion and if the liquid compositionlies to the right of the eutectic points identified as “A,” thenliquid-solid equilibrium principles suggest that the solid portion willbe pure DAS. Our processes, depicted representatively in FIG. 3, aredesigned to operate to the left of the eutectic points identified as “A”and, therefore, are expected to produce pure MAS.

Henceforth, representative processes are described with respect to FIGS.3 and 6. Typically, stream 100 is representative of point “P,” which isa DAS containing broth at about 5 wt %. In the reactiveevaporation/distillation step 102, water and ammonia areevaporated/distilled to form a 10 wt % MAS containing solution,typically, which is represented by point “Q.” Subsequently, in theconcentration unit 108, the MAS containing solution is concentrated toform a 60 wt % MAS containing solution, typically, which is representedby point “R.” Finally, the 60 wt % MAS containing solution is cooled (byevaporation, indirect contact cooling, or by a combination thereof) toproduce an approximately 37 wt % MAS containing liquid portionrepresented by point “S” in contact with a solid portion. According toliquid-solid equilibrium principles, our FIG. 6 shows that the solidportion will be essentially pure MAS that is substantially free of DASsince we typically operate our processes to the left of the eutecticpoints.

FIG. 7 is a microphotograph showing representative MAS crystals producedin accordance with our methods. Similarly, FIG. 8 is a microphotographof representative SA crystals produced in accordance with our methods.The micrographs demonstrate that MAS has a crystal shape that isdistinct from that of SA. Henceforth, we have shown that we can produceessentially pure MAS that is both substantially free of DAS and SA usingour methods.

EXAMPLES

The processes are illustrated by the following non-limitingrepresentative examples. In a number of the examples, a synthetic,aqueous DAS solution was used in place of an actual clarifiedDAS-containing fermentation broth. Other examples use an actualclarified DAS-containing fermentation broth.

The use of a synthetic DAS solution is believed to be a good model forthe behavior of an actual broth in our processes because of thesolubility of the typical fermentation by-products found in actualbroth. The major by-products produced during fermentation are ammoniumacetate, ammonium lactate and ammonium formate. If these impurities arepresent during the distillation step, one would not expect them to loseammonia and form free acids in significant quantities until all of theDAS had been converted to MAS. This is because acetic acid, lactic acidand formic acid are stronger acids than the second acid group of SA(pKa=5.48). In other words, acetate, lactate, formate and evenmonohydrogen succinate are weaker bases than the dianion succinate.Furthermore, ammonium acetate, ammonium lactate and ammonium formate aresignificantly more soluble in water than MAS, and each is typicallypresent in the broth at less than 10% of the DAS concentration. Inaddition, even if the acids (acetic, formic and lactic acids) wereformed during the distillation step, they are miscible with water andwill not crystallize from water. This means that the MAS reachessaturation and crystallizes from solution (i.e., forming the solidportion), leaving the acid impurities dissolved in the mother liquor(i.e., the liquid portion).

Example 1

This example demonstrates conversion of a portion of DAS into MAS viadistillation and recovery of MAS solids from distillation bottoms liquidvia cooling-induced crystallization.

A three neck 500 mL round bottom flask was fitted with a thermometer andDean Stark trap topped with a reflux condenser. The vent from the refluxcondenser went to a scrubbing bottle which contained 100 g of a 1.4Macetic acid solution. The flask was charged with 400 g of a 10% DASaqueous solution (pH 8.5). The contents of the flask were stirred with amagnetic stirrer and heated with a heating mantle to distill off 320.6 gof distillate (an aqueous ammonia solution) which was removed via theDean Stark trap. Analysis of the distillate indicated that about 20% ofthe contained ammonia had been removed from the charged DAS duringdistillation (i.e., the salts in the bottoms liquid were about 40% MASand about 60% DAS). Only traces of ammonia were found in the scrubbingbottle. The final temperature of the pot as the last drop distilled overwas 110° C. The residue (bottoms liquid) in the pot (73.4 g which wasabout 53% water) was placed in a flask and allowed to cool to roomtemperature overnight. Upon cooling to room temperature, white needlesof MAS were formed. The white solids were separated via vacuumfiltration, yielding 14 g of wet crystals (solid portion) and 56 g ofmother liquor (liquid portion). A portion of the wet crystals (7 g) wasdried overnight in a vacuum oven, yielding 6 g of dried solids whichcontained 0.4% water as determined by Karl-Fisher analysis. Analysis ofthe solids portion with HPLC revealed that the solids portion was freeof non-MAS nitrogen-containing impurities (e.g., succinimide andsuccinamide).

Example 2

This example demonstrates mother liquor recycle.

A 1-L round bottom flask was charged with 800 g of a synthetic 4.5% DASsolution, and then a distillation head was attached to the flask. Thecontents of the flask were distilled at atmospheric pressure leaving 67g of residue (bottoms liquid) in the flask. The bottoms liquid containedapproximately 45% water. Ammonia analyses of the distillates indicatethat the first distillation cycle removed about 29% of the ammonia,making a 42/58 mol/mol mixture of DAS and MAS. The residue (bottomsliquid) was then removed from the flask and placed in a beaker equippedwith a water bath. The beaker contents were cooled to 20° C. withstirring. Once the residue reached 20° C., it was seeded with a fewcrystals of MAS and allowed to stir for 30 minutes. The temperature ofthe bath was then lowered to 15° C. and held for 30 minutes. Thetemperature was then lowered to 10° C. and held for 30 minutes. Thetemperature was then cooled to 5° C. and held for 30 minutes and finallyto 0° C. where it was held for 30 minutes. The slurry (consisting ofsolid and liquid portions) was then quickly filtered using a pre-cooledsintered glass filter funnel and vacuum flask. The solids were dried ina vacuum oven yielding 13.9 g of dry MAS solids. The mother liquor(liquid portion, 47.2 g) was then combined with 800 g of synthetic 4.5%DAS solution and distilled, leaving 86.6 g of residue (bottoms liquid).In the second distillation (i.e., mother liquor recycle run) about 28%of the ammonia from the total amount of DAS present was removed. Theresidue (bottoms liquid) was then cooled (crystallized) in a similarmanner. However, the solution became cloudy at 46° C., so it was seededat 46° C. and allowed to slowly cool to room temperature overnight whilestirring. The next day the temperature was slowly ramped down by 5° C.increments to 0° C. The slurry (solid and liquid portions) was filteredas before, and the solids dried, yielding 23.5 g of MAS solids. This isequal to about a 75% recovery of the SA equivalents in the 800 g offresh DAS solution distilled. The recovered solids from the first cyclewere 95% MAS (about 5% water). In the second cycle, the solids were 97%MAS (about 3% water). The mother liquor from the second cycle contained28.8% SA equivalents (i.e., as SA salts).

Example 3

This example demonstrates the absence of amide and imide species in thesolid portion of cooled distillation bottoms.

A 1-L round bottom flask was charged with 800 g of a synthetic 4.5% DASsolution. The flask was fitted with a five tray 1″ Oldershaw sectionwhich was capped with a distillation head. The distillate was collectedin an ice cooled receiver. The contents of the flask were heated with aheating mantel and stirred with a magnetic stirrer. The contents of theflask were distilled giving 721.1 g of an overhead distillate and 72.2 gof a liquid residue in the flask (i.e. distillation bottoms). Theaqueous ammonia distillate was titrated revealing a 0.34% ammoniacontent (i.e., about 55% conversion of DAS to MAS). The hot distillationbottoms (approximately 47% salt solution of DAS and MAS) were thenplaced in a 125 mL Erlenmeyer flask and allowed to cool slowly to roomtemperature while stirring over night. The next morning the cloudysolution was cooled to 15° C. and held for 60 minutes, then cooled to10° C. and held for 60 minutes and finally cooled to 5° C. and held for60 minutes while stirring. The resulting white slurry was filteredyielding 12.9 g of wet crystals and 55.3 g of mother liquor. Thecrystals were dissolved in 25.8 g of distilled water. HPLC analysis ofthe crystal solution revealed no detectable amounts of amide or imidespecies. However, HPLC analysis of the mother liquor revealed a trace ofsuccinamic acid, but no detectable succinamide or succinimide.

Example 4

This example produces a solid portion of a cooled distillation bottomsthat consists essentially of MAS and is substantially free of DAS.

A three neck 1-L round bottom flask was fitted with an addition funneland a 1″ five tray Oldershaw column which was capped with a distillationhead. An ice cooled receiver was used to collect the distillate. Theflask was charged with 800 g of a synthetic 4.5% DAS solution. Thecontents of the flask were heated with a heating mantel and stirred witha magnetic stirrer. Distillation was started. While the distillationoccurred an additional 1600 g of the 4.5% DAS solution was slowly addedto the flask at the same rate as distillate was taken. A total of 2135 gof distillate was taken overhead. Titration of the distillate revealedthe overhead was a 0.33% ammonia solution. The hot aqueous distillationbottoms (253.8 g) was removed from the flask and placed in an Erlenmeyerflask. The distillation bottoms were allowed to slowly cool to roomtemperature while stirring overnight. The contents of the flask wereseeded and allowed to stir for 30 minutes. The slurry was then cooled to15° C. and held for 60 minutes, then 10° C. and held for 60 minutes andfinally to 5° C. and held for 60 minutes all while stirring. The slurrywas filtered cold and the solids (i.e., the solid portion) washed threetimes with about 20 g portions of a cold (about 5 C.) 20% sodiumchloride solution to displace the mother liquor (i.e., the liquidportion). Air was sucked through the cake for several minutes to removeas much liquid as possible. The solids were then dried in a vacuum ovenat 75° C. for one hour yielding 7.2 g of white crystals. Carbon andnitrogen analyses of the solids revealed a 4.06 atomic ratio of carbonto nitrogen (i.e., a 1.01 ratio of ammonia to SA or about 99% MAS). Thata ratio of 1.00 was not obtained is believed to be attributable toincomplete washing of the solids.

Example 5

This example demonstrates the effect of solvents on ammonia evolutionfrom aqueous DAS. Run 5 is the control experiment where no solvent ispresent.

The outer necks of a three neck 1-L round bottom flask were fitted witha thermometer and a stopper. The center neck was fitted with a five tray1″ Oldershaw section. The Oldershaw section was topped with adistillation head. An ice cooled 500 mL round bottom flask was used asthe receiver for the distillation head. The 1-L round bottom flask wascharged with distilled water, the solvent being tested, SA andconcentrated ammonium hydroxide solution. The contents were stirred witha magnetic stirrer to dissolve all the solids. After the solidsdissolved, the contents were heated with the heating mantle to distill350 g of distillate. The distillate was collected in the ice cooled 500mL round bottom flask. The pot temperature was recorded as the last dropof distillate was collected. The pot contents were allowed to cool toroom temperature and the weight of the residue and weight of thedistillate were recorded. The ammonia content of the distillate was thendetermined via titration. The results were recorded in Table 1.

TABLE 1 Run # 1 2 3 4 5 Name of Acid charged Succinic Succinic SuccinicSuccinic Succinic Wt Acid Charged (g) 11.81 11.79 11.8 11.79 11.8 MolesAcid Charged 0.1 0.1 0.1 0.1 0.1 Wt 28% NH3 Solution Charged (g) 12.1112.09 12.1 12.11 12.1 Moles NH3 Charged 0.2 0.2 0.2 0.2 0.2 Name ofSolvent Diglyme PG* GBL** butoxy none triglycol Wt Solvent Charged (g)400 400.1 400 400 0 Wt Water Charged (g) 400 400 400 400 800 WtDistillate (g) 350.5 351.6 350.1 350.7 351 Wt Residue (g) 466.3 461.7464.3 460.9 466 % Mass Accountability 99.1 98.7 98.9 98.5 99.2 Wt % NH3in distillate (titration) 0.48 0.4 0.27 0.47 0.13 Moles NH3 indistillate 0.099 0.083 0.056 0.097 0.027 % NH3 removed in Distillate49.5 42 28 49 13.4 % First NH3 removed in Distillate 99 84 56 98 27 %Second NH3 removed in 0 0 0 0 0 Distillate Final Pot Temp (° C.) 101 120110 107 100 *PG is propylene glycol **GBL is gamma butyrolactone

Example 6

This example produced a solid portion from a cooled distillation bottomsthat consists essentially of SA and is substantially free of MAS.

A 300 mL Parr autoclave was charged with 80 g of synthetic MAS and 120 gof water. The autoclave was sealed and the contents stirred and heatedto ˜200° C. at an autogenic pressure of ˜190 psig. Once the contentsreached temperature, water was fed to the autoclave at a rate of ˜2g/min and vapor removed from the autoclave at a rate of ˜2 g/min with aback pressure regulator. Vapor exiting the autoclave was condensed andcollected in a receiver. The autoclave was run under these conditionsuntil a total of 1020 g of water had been fed and a total of 1019 g ofdistillate collected. The distillate was titrated for ammonia content(0.29% ammonia by weight). This translates into a ˜29% conversion of MASto SA. The contents of the autoclave (194.6 g) were partially cooled anddischarged from the reactor. The slurry was allowed to stand understirring at room temperature over night in an Erlenmeyer flask. Theslurry was then filtered and the solids rinsed with 25 g of water. Themoist solids were dried in a vacuum oven at 75° C. for 1 hr yielding 9.5g of SA product. Analysis via an ammonium ion electrode revealed 0.013mmole ammonium ion/g of solid. HPLC analysis revealed the solids were SAwith 0.8% succinamic acid impurity.

Example 7

This example used DAS-containing clarified fermentation broth derivedfrom a fermentation broth containing E. Coli strain ATCC PTA-5132. Thisexample produced a solid portion of a cooled distillation bottoms thatconsists essentially of MAS and is substantially free of DAS.

A three neck 1-L round bottom flask was fitted with an addition funneland a 1″ five tray Oldershaw column which was capped with a distillationhead. An ice cooled receiver was used to collect the distillate. Theflask was charged with 800 g of clarified DAS-containing fermentationbroth which contained 4.4% DAS, 1% ammonium acetate, 0.05% ammoniumformate and 0.03% ammonium lactate. The contents of the flask wereheated with a heating mantel and stirred with a magnetic stirrer.Distillation was started. While the distillation ran, an additional 2200g of the broth solution was slowly added to the flask at the same rateas distillate was removed. A total of 2703 g of distillate was taken asoverhead. Titration of the distillate revealed the overhead was a 0.28%ammonia solution. The hot aqueous distillation bottoms solution (269.7g) was removed from the flask and placed in an Erlenmeyer flask. Thedistillation bottoms were allowed to slowly cool to room temperaturewhile stirring overnight. The next day, the contents of the flask wereseeded and allowed to stir for 30 minutes. The slurry was then cooled to15° C. and held for 30 minutes, then to 10° C. and held for 30 minutesand finally to 5° C. and held for 30 minutes, all while stirring. Theslurry was filtered cold and air was sucked through the cake for severalminutes to remove as much liquid as possible. Light brown solids (72.5g) and dark brown mother liquor (188.4 g with a pH of 6.4) wereobtained. The solids were recrystallized to remove the mother liquor bydissolution in 72 g of water at 50° C. The solution was then allowed toslowly cool to room temperature while stirring overnight. The next daythe contents of the flask were seeded and stirred for 30 minutes. Theslurry was then cooled to 15° C. and held for 30 minutes, then to 10° C.and held for 30 minutes, and finally to 5° C. and held for 30 minutes,all while stirring. The slurry was filtered cold and air was suckedthrough the cake for several minutes to remove as much liquid aspossible, yielding 110 g of brown mother liquor (pH 5.0). The solidswere then dried in a vacuum oven at 75° C. for one hour yielding 24 g ofoff-white crystals. Carbon and nitrogen analyses of the solids revealeda 4.04 molar ratio of carbon to nitrogen (i.e. a 1.01 ratio of ammoniato SA or ˜99% MAS). HPLC analysis revealed that the MAS contained 0.07%succinamic acid but no detectable succinamide, succinimide or acetatespecies. In other words, the MAS was free of DAS and otherwisesubstantially pure.

Example 8

This example used fermentation derived MAS from a fermentation brothcontaining E. Coli strain ATCC PTA-5132. This example produced a solidportion from a cooled distillation bottoms that consists essentially ofSA and is substantially free of MAS.

A 300 mL Parr autoclave was charged with 80 g of broth derived MAS and120 g of water. The autoclave was sealed and the contents stirred andheated to ˜202° C. at an autogenic pressure of ˜205 psig. Once thecontents reached temperature, water was fed to the autoclave at a rateof ˜2 g/min and vapor was removed from the autoclave at a rate of ˜2g/min with a back pressure regulator. Vapor exiting the autoclave wascondensed and collected in a receiver. The autoclave was run under theseconditions until a total of 905 g of water had been fed and a total of908 g of distillate collected. The distillate was titrated for ammoniacontent (0.38% ammonia by weight). This translates into a ˜34%conversion of MAS to SA. The contents of the autoclave (178.2 g) werepartially cooled and discharged from the reactor. The slurry was allowedto stand under stirring at room temperature over night in an Erlenmeyerflask. The slurry was then filtered and the solids rinsed with 25 g ofwater. The moist solids were dried in a vacuum oven at 75° C. for 1 hryielding 8.5 g of SA product. Analysis via an ammonium ion electroderevealed 0.027 mmole ammonium ion/g of solid. HPLC analysis revealed thesolids were SA with 1.4% succinamic acid and 0.1% succinamideimpurities.

Example 9

This example used an ammonia releasing solvent to aid deammoniation.This example produced a solid portion from a cooled distillation bottomsthat consists essentially of SA and is substantially free of MAS.

A 500 mL round bottom flask was charged with 29 g of MAS solids, 51 g ofwater and 80 g of triglyme. The flask was fitted with a 5 tray 1″ glassOldershaw column section which was topped with a distillation head. Anaddition funnel containing 2500 g of water was also connected to theflask. The flask was stirred with a magnetic stirrer and heated with aheating mantel. The distillate was collected in an ice cooled receiver.When the distillate started coming over the water in the addition funnelwas added to the flask at the same rate as the distillate was beingtaken. A total of 2491 g of distillate was taken. The distillatecontained 2.3 g of ammonia, as determined by titration. This means ˜63%of the MAS was converted to SA. The residue in the flask was then placedin an Erlenmeyer flask and cooled to −5° C. while stirring. Afterstirring for 30 minutes the slurry was filtered while cold yielding 15.3g of solids. The solids were dissolved in 15.3 g of hot water and thencooled in an ice bath while stirring. The cold slurry was filtered andthe solids dried in a vacuum oven at 100° C. for 2 hrs yielding 6.5 g ofsuccinic acid. HPLC analysis indicated that the solids were SA with0.18% succinamic acid present.

Example 10

This example used an ammonia releasing solvent to aid deammoniation.This example produced a solid portion of a cooled distillation bottomsthat consists essentially of MAS and is substantially free of DAS.

A 500 mL round bottom flask was charged with 80 g of an aqueous 36% DASsolution and 80 g of triglyme. The flask was fitted with a 5 tray 1″glass Oldershaw column section which was topped with a distillationhead. An addition funnel containing 700 g of water was also connected tothe flask. The flask was stirred with a magnetic stirrer and heated witha heating mantel. The distillate was collected in an ice cooledreceiver. When the distillate started coming over the water in theaddition funnel was added to the flask at the same rate as thedistillate was being taken. A total of 747 g of distillate was taken.The distillate contained 3.7 g of ammonia, as determined by titration.This means ˜57% of the ammonia was removed. In other words, all of theDAS was converted into MAS and ˜14% of the MAS was further convertedinto SA. The residue in the flask was then placed in an Erlenmeyer flaskand cooled to 5° C. while stirring. After stirring for 30 minutes theslurry was filtered while cold and the solids dried in a vacuum oven at100° C. for 2 hrs yielding 10.3 g of MAS. Analysis indicated that thesolids were MAS with 0.77% succinamic acid and 0.14% succinimidepresent.

Example 11

This example demonstrates the use of an azeotroping solvent,particularly separation of MAS from other by-products in the broth.

A three neck 500 mL round bottom flask was fitted with a thermometer, a250 mL addition funnel and a Dean Stark trap topped with a refluxcondenser. The flask was charged with 100 g of toluene and 100 g of a˜9% DAS broth solution (which also contained about 1% ammonium acetateand ammonium formate combined). The addition funnel was charged with 250g of the 9% diammonim succinate broth solution. The contents of theflask were stirred with a magnetic stirrer and heated with a heatingmantel bringing the contents to boil. The contents of the additionfunnel were added slowly to the flask allowing the toluene-waterazeotope to distill into the Dean-Stark trap with return of the tolueneto the flask. After all the contents of the addition funnel had beenadded (at a rate substantially equal to the distillate) the contentswere allowed to further reflux until a total of 277.5 g of aqueous phasehad been collected from the Dean Stark trap. The contents of the flaskwere removed while hot and the two phases separated in a warm reparatoryfunnel. The aqueous phase was cooled in an ice bath while being stirred.The resulting solids were recovered via filtration using a sinteredglass funnel. The mother liquor was dark brown and the filtered solidswere off-white. The solids were dried in a vacuum oven and analyzed viaHPLC. The dried solids (5.7 g) were ˜96% monoammonium succinate and ˜1%ammonium acetate with the rest being water.

Example 12

A pressure distillation column was constructed using an 8 ft long 1.5″316 SS Schedule 40 pipe packed with 316 SS Propak packing. The base ofthe column was equipped with an immersion heater to serve as thereboiler. Nitrogen was injected into the reboiler via a needle valve topressure. The overhead of the column had a total take-off line whichwent to a 316 SS shell and tube condenser with a receiver. The receiverwas equipped with a pressure gauge and a back pressure regulator.Material was removed from the overhead receiver via blowcasing through aneedle valve. Preheated feed was injected into the column at the top ofthe packing via a pump. Preheated water was also injected into thereboiler via a pump. This column was operated at 30 psig pressure whichgave a column temperature of 137° C. The top of the column was fed asynthetic 10% DAS solution at a rate of 5 mL/min and water was fed tothe reboiler at a rate of 5 mL/min. The overhead distillate rate was 8mL/min and the residue rate was 2 mL/min. Titration of the distillatefor ammonia indicated that the ˜47% of the ammonia had been removed inthe distillate (i.e. the conversion to MAS was ˜94%). The residue liquidwas ˜20% MAS and HPLC analysis of the residue indicated an ˜3%inefficiency to succinamic acid.

Example 13

A portion of the residue (800 g) from Example 12 was concentrated via abatch distillation to ˜59% MAS solution (i.e. 530 g of water wasdistilled off). The residue was then cooled to 5° C. while stirring. Theresulting slurry was filtered and the solids dried in a vacuum oven at75° C. for 1 hour yielding 52.5 g of MAS solids (i.e. ˜32% recovery).HPLC analysis indicated that the solids contained 0.49% succinamic acidand no succinimide.

Example 14

A second portion of the pressure column residue (3200 g) from Example 12was placed in the evaporative crystallizer and concentrated to ˜72% MASby distilling off 2312 g of water at 60° C. under vacuum. The resultinghot slurry was centrifuged and the recovered solids dried in the vacuumoven at 75° C. for one hour yielding 130.7 g of MAS solids. The motherliquor from the centrifuging step was allowed to cool to roomtemperature forming a second crop of crystals. This slurry was filteredand the recovered solids were dried at 75° C. under vacuum yielding114.8 g of MAS solids. Based on the succinate concentration of the feedto the crystallizer, a 20% and 18% recovery was realized for the firstand second crops, respectively (i.e. a 38% overall recovery). HPLCanalysis of the two crops of solids indicated that the first crop had nodetectable succinamic acid and succinimide while the second crop had0.96% succinamic acid and 0.28% succinimide.

Comparative Example 1

This example demonstrates that an atmospheric distillation of an aqueousMAS solution removes very little ammonia when triglyme is not present.

A 500 mL round bottom flask was charged with 30 g of MAS solids and 120g of water. The flask was fitted with a 5 tray 1″ glass Oldershaw columnsection which was topped with a distillation head. An addition funnelcontaining 600 g of water was also connected to the flask. The flask wasstirred with a magnetic stirrer and heated with a heating mantel. Thedistillate was collected in an ice cooled receiver. When the distillatestarted coming over the water in the addition funnel was added to theflask at the same rate as the distillate was being taken. A total of 606g of distillate was taken. The distillate contained 0.15 g of ammonia,as determined by titration. This means ˜4% of the MAS was converted toSA.

Comparative Example 2

This example demonstrates the decrease in ammonia removal for DAS whentriglyme is not present.

A 500 mL round bottom flask was charged with 80 g of an aqueous 36% DASsolution and 80 g of water. The flask was fitted with a 5 tray 1″ glassOldershaw column section which was topped with a distillation head. Anaddition funnel containing 1200 g of water was also connected to theflask. The flask was stirred with a magnetic stirrer and heated with aheating mantel. The distillate was collected in an ice cooled receiver.When the distillate started coming over the water in the addition funnelwas added to the flask at the same rate as the distillate was beingtaken. A total of 1290 g of distillate was taken. The distillatecontained 2.2 g of ammonia, as determined by titration. This means ˜44%of the DAS was converted to MAS.

Although our processes have been described in connection with specificsteps and forms thereof, it will be appreciated that a wide variety ofequivalents may be substituted for the specified elements and stepsdescribed herein without departing from the spirit and scope of thisdisclosure as described in the appended claims.

1. A process for making MAS from a clarified DAS-containing fermentation broth comprising: (a) distilling the broth to form an overhead that comprises water and ammonia, and a liquid bottoms that comprises MAS, at least some DAS, and at least about 20 wt % water; (b) cooling and/or evaporating the bottoms, and optionally adding an antisolvent to the bottoms, to attain a temperature and composition sufficient to cause the bottoms to separate into a DAS-containing liquid portion and a MAS-containing solid portion that is substantially free of DAS; (c) separating the solid portion from the liquid portion; and (d) recovering the solid portion.
 2. The process of claim 1, wherein the solid portion is substantially free of succinamic acid, succinamide and succinimide.
 3. The process of claim 1, wherein distilling the broth is carried out in the presence of an ammonia separating solvent which is at least one selected from the group consisting of diglyme, triglyme, tetraglyme, sulfoxides, amides, sulfones, polyethyleneglycol (PEG), gamma butyrolactone, butoxytriglycol, N-methylpyrolidone (NMP), ethers, and methyl ethyl ketone (MEK) or in the presence of a water azeotroping solvent which is at least one selected from the group consisting of toluene, xylene, methylcyclohexane, methyl isobutyl ketone, hexane, cyclohexane and heptane.
 4. The process of claim 1, further comprising removing water from the liquid bottoms to increase concentration of MAS in the liquid bottoms.
 5. The process of claim 1, wherein cooling the bottoms comprises cooling the liquid bottoms in a first stage at 50-70° C., cooling the liquid bottoms at a second stage at 30-50° C. and cooling the liquid bottoms at a third stage at 10-30° C.
 6. A process for making SA from a clarified DAS-containing fermentation broth, comprising: (a) distilling the broth to form a first overhead that comprises water and ammonia, and a first liquid bottoms that comprises MAS, at least some DAS, and at least about 20 wt % water; (b) cooling and/or evaporating the first bottoms, and optionally adding an antisolvent to the first bottoms, to attain a temperature and composition sufficient to cause the first bottoms to separate into a DAS-containing first liquid portion and a MAS-containing first solid portion that is substantially free of DAS; (c) separating the first solid portion from the first liquid portion; (d) recovering the first solid portion; (e) dissolving the first solid portion in water to produce an aqueous MAS solution; (f) distilling the aqueous MAS solution at a temperature and pressure sufficient to form a second overhead that comprises water and ammonia, and a second bottoms that comprises a major portion of SA, a minor portion of MAS, and water; (g) cooling and/or evaporating the second bottoms to cause the second bottoms to separate into a second liquid portion and a second solid portion that consists essentially of SA and is substantially free of MAS; (h) separating the second solid portion from the second liquid portion; and (i) recovering the second solid portion.
 7. The process of claim 6, wherein the first and second solid portions are substantially free of succinamic acid, succinamide and succinimide.
 8. The process of claim 6, wherein distilling the broth and/or the MAS solution is carried out in the presence of an ammonia separating solvent which is at least one selected from the group consisting of diglyme, triglyme, tetraglyme, sulfoxides, amides, sulfones, polyethyleneglycol (PEG), gamma butyrolactone, butoxytriglycol, N-methylpyrolidone (NMP), ethers, and methyl ethyl ketone (MEK) or in the presence of a water azeotroping solvent which is at least one selected from the group consisting of toluene, xylene, methylcyclohexane, methyl isobutyl ketone, hexane, cyclohexane and heptane.
 9. The process of claim 6, further comprising removing water from the first liquid bottoms to increase concentration of MAS in the first liquid bottoms and from the second liquid bottoms to increase concentration of SA in the second liquid bottoms.
 10. The process of claim 6, wherein cooling the bottoms comprises cooling the liquid bottoms in a first stage at 50-70° C., cooling the liquid bottoms at a second stage at 30-50° C. and cooling the liquid bottoms at a third stage at 10-30° C.
 11. A process for making MAS from a clarified MAS-containing fermentation broth comprising: (a) optionally adding at least one of MAS, DAS, SA, NH₃, and NH₄ ⁺, to the broth depending on pH of the broth; (b) distilling the broth to form an overhead that comprises water and optionally ammonia and a liquid bottoms that comprises MAS, at least some DAS, and at least about 20 wt % water; (c) cooling and/or evaporating the bottoms, and optionally adding an antisolvent to the bottoms, to attain a temperature and composition sufficient to cause the bottoms to separate into a DAS-containing liquid portion and a MAS-containing solid portion that is substantially free of DAS; (d) separating the solid portion from the liquid portion; and (e) recovering the solid portion.
 12. The process of claim 11, wherein the solid portion are substantially free of succinamic acid, succinamide and succinimide.
 13. The process of claim 11, wherein distilling the broth is carried out in the presence of an ammonia separating solvent which is at least one selected from the group consisting of diglyme, triglyme, tetraglyme, sulfoxides, amides, sulfones, polyethyleneglycol (PEG), gamma butyrolactone, butoxytriglycol, N-methylpyrolidone (NMP), ethers, and methyl ethyl ketone (MEK) or in the presence of a water azeotroping solvent which is at least one selected from the group consisting of toluene, xylene, methylcyclohexane, methyl isobutyl ketone, hexane, cyclohexane and heptane.
 14. The process of claim 11, further comprising removing water from the liquid bottoms to increase concentration of MAS in the liquid bottoms.
 15. The process of claim 11, wherein cooling the bottoms comprises cooling the liquid bottoms in a first stage at 50-70° C., cooling the liquid bottoms at a second stage at 30-50° C. and cooling the liquid bottoms at a third stage at 10-30° C.
 16. A process for making SA from a clarified MAS-containing fermentation broth comprising: (a) optionally adding at least one of MAS, DAS, SA, NH₃, and NH₄ ⁺, to the broth depending on pH of the broth; (b) distilling the broth to form an first overhead that comprises water and, optionally, ammonia and a first liquid bottoms that comprises MAS, at least some DAS, and at least about 20 wt % water; (c) cooling and/or evaporating the first bottoms, and optionally adding an antisolvent to the first bottoms, to attain a temperature and composition sufficient to cause the first bottoms to separate into a DAS-containing first liquid portion and a MAS-containing first solid portion that is substantially free of DAS; (d) separating the first solid portion from the first liquid portion; (e) dissolving the first solid portion in water to produce an aqueous MAS solution; (f) distilling the aqueous MAS solution at a temperature and pressure sufficient to form a second overhead that comprises water and ammonia, and a second bottoms that comprises a major portion of SA, a minor portion of MAS, and water; (g) cooling and/or evaporating the second bottoms to cause the second bottoms to separate into a second liquid portion and a second solid portion that consists essentially of SA and is substantially free of MAS; (h) separating the second solid portion from the second liquid portion; and (i) recovering the second solid portion.
 17. The process of claim 16, wherein the first and second solid portions are substantially free of succinamic acid, succinamide, and succinimide.
 18. The process of claim 16, wherein distilling the broth and/or the MAS solution is carried out in the presence of an ammonia separating solvent which is at least one selected from the group consisting of diglyme, triglyme, tetraglyme, sulfoxides, amides, sulfones, polyethyleneglycol (PEG), gamma butyrolactone, butoxytriglycol, N-methylpyrolidone (NMP), ethers, and methyl ethyl ketone (MEK) or in the presence of a water azeotroping solvent which is at least one selected from the group consisting of toluene, xylene, methylcyclohexane, methyl isobutyl ketone, hexane, cyclohexane and heptane.
 19. The process of claim 16, further comprising removing water from the first liquid bottoms to increase concentration of MAS in the first liquid bottoms and from the second liquid bottoms to increase concentration of SA in the second liquid bottoms.
 20. The process of claim 16, wherein cooling the bottoms comprises cooling the liquid bottoms in a first stage at 50-70° C., cooling the liquid bottoms at a second stage at 30-50° C. and cooling the liquid bottoms at a third stage at 10-30° C.
 21. A process for making MXS from a clarified DAS-containing fermentation broth, where X is at least one of NH₄ ⁺, Na⁺ and K⁺ comprising: (a) distilling the broth to form an overhead that comprises water and ammonia, and a liquid bottoms that comprises MXS, at least some DYS where DYS comprises DAS and at least one of DNaS and DKS, and at least about 20 wt % water; (b) cooling and/or evaporating the bottoms, and optionally adding an antisolvent to the bottoms, to attain a temperature and composition sufficient to cause the bottoms to separate into a DYS-containing liquid portion and a MXS-containing solid portion that is substantially free of DYS; (c) separating the solid portion from the liquid portion; and (d) recovering the solid portion.
 22. The process of claim 21, wherein the solid portion is substantially free of succinamic acid, succinamide and succinimide.
 23. The process of claim 21, wherein distilling the broth is carried out in the presence of an ammonia separating solvent which is at least one selected from the group consisting of diglyme, triglyme, tetraglyme, sulfoxides, amides, sulfones, polyethyleneglycol (PEG), gamma butyrolactone, butoxytriglycol, N-methylpyrolidone (NMP), ethers, and methyl ethyl ketone (MEK) or in the presence of a water azeotroping solvent which is at least one selected from the group consisting of toluene, xylene, methylcyclohexane, methyl isobutyl ketone, hexane, cyclohexane and heptane.
 24. The process of claim 21, further comprising removing water from the liquid bottoms to increase concentration of MXS in the liquid bottoms.
 25. The process of claim 21, wherein cooling the bottoms comprises cooling the liquid bottoms in a first stage at 50-70° C., cooling the liquid bottoms at a second stage at 30-50° C. and cooling the liquid bottoms at a third stage at 10-30° C.
 26. A process for making MXS from a clarified MXS-containing fermentation broth, where X is at least one of NH₄ ⁺, Na⁺ and K⁺ comprising: (a) optionally adding at least one of SA, NH₃, NH₄ ⁺, Na⁺, and K⁺ to the broth depending on pH of the broth; (b) distilling the broth to form an overhead that comprises water and optionally ammonia and a liquid bottoms that comprises MXS, at least some DYS where DYS comprises at least one of DAS, DNaS and DKS, and at least about 20 wt % water; (c) cooling and/or evaporating the bottoms, and optionally adding an antisolvent to the bottoms, to attain a temperature and composition sufficient to cause the bottoms to separate into a DYS-containing liquid portion and a MXS-containing solid portion that is substantially free of DYS; (d) separating the solid portion from the liquid portion; and (e) recovering the solid portion.
 27. The process of claim 26, wherein the solid portion are substantially free of succinamic acid, succinamide and succinimide.
 28. The process of claim 26, wherein distilling the broth is carried out in the presence of an ammonia separating solvent which is at least one selected from the group consisting of diglyme, triglyme, tetraglyme, sulfoxides, amides, sulfones, polyethyleneglycol (PEG), gamma butyrolactone, butoxytriglycol, N-methylpyrolidone (NMP), ethers, and methyl ethyl ketone (MEK) or in the presence of a water azeotroping solvent which is at least one selected from the group consisting of toluene, xylene, methylcyclohexane, methyl isobutyl ketone, hexane, cyclohexane and heptane.
 29. The process of claim 26, further comprising removing water from the liquid bottoms to increase concentration of MXS in the liquid bottoms.
 30. The process of claim 26, wherein cooling the bottoms comprises cooling the liquid bottoms in a first stage at 50-70° C., cooling the liquid bottoms at a second stage at 30-50° C. and cooling the liquid bottoms at a third stage at 10-30° C.
 31. A process for making MgS from a clarified DAS-containing fermentation broth comprising: (a) distilling the broth to form an overhead that comprises water and ammonia, and a liquid bottoms that comprises MgS, at least some DYS where DYS comprises DAS and MgS, and at least about 20 wt % water; (b) cooling and/or evaporating the bottoms, and optionally adding an antisolvent to the bottoms, to attain a temperature and composition sufficient to cause the bottoms to separate into a DAS and MgS containing liquid portion and a MgS-containing solid portion that is substantially free of DYS; (c) separating the solid portion from the liquid portion; and (d) recovering the solid portion.
 32. The process of claim 31, wherein the solid portion is substantially free of succinamic acid, succinamide and succinimide.
 33. The process of claim 31, wherein distilling the broth is carried out in the presence of an ammonia separating solvent which is at least one selected from the group consisting of diglyme, triglyme, tetraglyme, sulfoxides, amides, sulfones, polyethyleneglycol (PEG), gamma butyrolactone, butoxytriglycol, N-methylpyrolidone (NMP), ethers, and methyl ethyl ketone (MEK) or in the presence of a water azeotroping solvent which is at least one selected from the group consisting of toluene, xylene, methylcyclohexane, methyl isobutyl ketone, hexane, cyclohexane and heptane.
 34. The process of claim 31, further comprising removing water from the liquid bottoms to increase concentration of MgS in the liquid bottoms.
 35. The process of claim 31, wherein cooling the bottoms comprises cooling the liquid bottoms in a first stage at 50-70° C., cooling the liquid bottoms at a second stage at 30-50° C. and cooling the liquid bottoms at a third stage at 10-30° C.
 36. A process for making MgS from a clarified MAS-containing fermentation broth comprising: (a) optionally adding at least one of SA, NH₃, NH₄ ⁺ and Mg⁺² to the broth depending on pH of the broth; (b) distilling the broth to form an overhead that comprises water and optionally ammonia and a liquid bottoms that comprises MgS, at least some MAS, and at least about 20 wt % water; (c) cooling and/or evaporating the bottoms, and optionally adding an antisolvent to the bottoms, to attain a temperature and composition sufficient to cause the bottoms to separate into a MAS-containing liquid portion and a MgS-containing solid portion that is substantially free of MAS; (d) separating the solid portion from the liquid portion; and (e) recovering the solid portion.
 37. The process of claim 36, wherein the solid portion are substantially free of succinamic acid, succinamide and succinimide.
 38. The process of claim 36, wherein distilling the broth is carried out in the presence of an ammonia separating solvent which is at least one selected from the group consisting of diglyme, triglyme, tetraglyme, sulfoxides, amides, sulfones, polyethyleneglycol (PEG), gamma butyrolactone, butoxytriglycol, N-methylpyrolidone (NMP), ethers, and methyl ethyl ketone (MEK) or in the presence of a water azeotroping solvent which is at least one selected from the group consisting of toluene, xylene, methylcyclohexane, methyl isobutyl ketone, hexane, cyclohexane and heptane.
 39. The process of claim 36, further comprising removing water from the liquid bottoms to increase concentration of MgS in the liquid bottoms.
 40. The process of claim 36, wherein cooling the bottoms comprises cooling the liquid bottoms in a first stage at 50-70° C., cooling the liquid bottoms at a second stage at 30-50° C. and cooling the liquid bottoms at a third stage at 10-30° C. 